A piece of equipment is known for scarifying roadways, clearing paths in a forest, or preparing ground for agricultural use which comprises a vehicle body adapted to travel along the ground in a horizontal travel direction, a drum mounted at a front end of the body and rotatable about a horizontal axis generally perpendicular to the direction, an array of radially outwardly projecting chisels mounted on the drum, and a plurality of angularly spaced breaker elements mounted on the drum between the chisels. As described in Austrian patent document 400,452 a breaker bar is mounted on the body spaced from the drum. When the drum is rotated such that its front side moves upward and its rear side moves downward the chisels and elements engage rocks on the ground, pick them up, and comminute them by crushing them against the breaker bar.
When used for clearing paths in, for example, a forest, this machine does not work well, as opposed to when used to scarify a concrete or macadam roadway. In nature the rocks that need to be cut back or crushed are of varying sizes, so the one-size-fits-all construction of the standard traveling crusher is often ineffective. When, for instance, a large rock is pulled by the chisels out of the ground, it can get wedged between the drum and the breaker bar unless same is set back relatively far, in which case smaller stones will pass through without being comminuted.